He has sharp eyes. He found this long-armed brittle star for us:
The central disc here is less than 1 cm across. The arms never stopped moving; it's hard to know how long they were.
We found a few more, some very tiny, under rocks at the low tide line. I picked one up and moved it to a sandy spot for a photo shoot. Watch what he does:
Stretched out on the sand, but already digging in.
5 seconds later.
10 more seconds. Almost hidden.
I caught him, before he disappeared completely...
And put him on a rock where he couldn't burrow.
When we had finished taking his picture, we replaced him on the sand and lowered his rock over him, very gently.